I want to talk to you about something that took me two decades of practice to fully understand — and that I believe is one of the most overlooked reasons dogs develop cancer.
It starts with something as ordinary as a collar and a leash.
I know that might sound surprising. But stay with me, because this is no longer just my clinical observation. In 2025, researchers confirmed what I have been seeing in my patients for twenty years: the nervous system plays a direct, active role in whether cancer starts, grows, and spreads in the body.
And the neck, the very place a collar sits, is one of the most important parts of that system.
A Pattern I Kept Seeing
When you practice integrative veterinary medicine long enough, certain patterns become impossible to ignore.
I started noticing years ago that dogs coming in with tumors in different parts of the body had something in common: a history of injury in the neck from collars or back pain in general.
The breeds I was seeing this in most often? Labs, Golden Retrievers, German Shepherds, Rottweilers. These are also the breeds most likely to be strong pullers on a leash. Coincidence? I stopped believing that a long time ago.
The connection between the toe tumors and the masses were one of the clearest patterns. The nerve chain that starts at the collar runs all the way down the front leg to the very tips of the toes — so tumors appearing right there, at the end of that pathway, started to make anatomical sense. But I was also seeing the same pattern in tumors near the head and neck, along the front legs, and in internal organs. These appeared to be connected to the energy and nerve lines of a particular spinal segment that was injured.
This is why I made it a consistent practice: whenever a dog came to me for an exam, I always assessed the neck and spine as part of the physical examination. Not as a curiosity but as a very useful diagnostic tool to determine, if I should do further imaging in the effort to rule out a possible tumour.
For many years I held this position based on my own clinical experience and the logic of anatomy alone. Then, in 2025, the science caught up.
What the Research Now Confirms
A major scientific review published in 2025 documented something that changes the way we think about cancer: the nervous system is not just a passenger in the cancer process. It is an active driver.
Here is what that means in plain language:
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- Tumors actively attract nerve fibers. Cancer literally reaches out to recruit nerves, and the more nerve fibers a tumor has growing into it, the more aggressive it tends to be.
- Chronic stress on the nervous system creates a "welcome environment" for cancer. When the nervous system is under prolonged strain from injury, inflammation, or disrupted signaling, it suppresses the immune cells that are supposed to detect and destroy abnormal cells before they become tumors.
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Damaged nerves can guide cancer cells. The support cells around injured nerve fibers can actually help malignant cells spread along nerve pathways, a mechanism now confirmed in multiple cancer types.
A separate 2026 review confirmed that the nervous system regulates tumor behavior both directly, by changing signals inside cancer cells, and indirectly, by reshaping the environment those cells live in.
And a 2025 study from MD Anderson Cancer Center showed that nerve injury leads to chronic inflammation and a kind of immune exhaustion, where the body's defences become too worn down to effectively fight cancer.
This is coming from some of the world's most respected cancer research centers.
Now, let's connect this to what happens inside a dog who has been walked on a collar for years.
What a Collar Actually Does to Your Dog's Body
Every time your dog pulls on a leash — and a collar presses against their neck — compressive force goes through the cervical spine. Do that thousands of times over months and years, and here is what builds up:
The vertebrae in the neck shift out of alignment.
This puts chronic pressure on the nerve roots exiting the spine — the very nerves that travel down the front legs, and also the vagus nerve, which is the body's main communication line between the brain and the heart, lungs, stomach, liver, and intestines.
The irritated nerves trigger a slow, quiet inflammation.
Compressed nerve roots release chemical messengers that create a low-grade inflammatory state in all the tissues those nerves supply. Your dog may show no outward signs of pain. But underneath, the body is living in a state of constant, low-level stress.
The vertebrae in the neck shift out of alignment. The immune system gradually loses its ability to patrol.
Blood flow to the extremities decreases. The immune cells that normally circulate through tissues — looking for abnormal cells and neutralizing them early — stop getting delivered effectively. Cancer researchers call this "impaired immune surveillance." In simple terms: the security system starts failing.
The vertebrae in the neck shift out of alignment. The conditions for cancer quietly take hold.
Chronic inflammation. Disrupted nerve signaling. Weakened local immunity. These are precisely the conditions that modern cancer research has now identified as necessary for tumors to start and grow — not just in the toe, but anywhere in the body whose nerve supply, blood flow, or immune surveillance has been undermined over time.
This is why I say: the nail bed tumor is simply the most visible, most anatomically direct expression of a pattern that can show up anywhere along the injured back, spine and nerves.
Traditional Chinese Medicine Knew This First
Traditional Chinese Medicine doesn't use words like "neurogenic inflammation" or "immune surveillance." But it has described this same pattern for thousands of years.
Collar trauma creates what TCM calls Qi and Blood stagnation in the cervical region — a blockage of energy and nourishment flowing to the tissues connected to those pathways.
What ancient medicine called stagnation, modern cancer neuroscience calls reduced blood flow, chronic inflammation, and failing local immunity.
Two entirely different frameworks. Thousands of years apart. Describing the same biological reality.
This Goes Well Beyond Toe Tumors
I want to be direct here, because this matters enormously.
Any dog with a long history of collar use and leash pulling has been accumulating stress on the cervical spine and nervous system — stress that may contribute to cancer risk anywhere in the body, not just at the toe.
Think about what sits right at collar level: the thyroid gland. The vagus nerve — which governs immune function in every major organ it reaches. The sympathetic nervous system — which, when chronically disrupted, has now been confirmed by multiple independent studies to create tumor-promoting conditions throughout the body.
This does not mean every dog wearing a collar will develop cancer. Genetics, diet, toxic exposures — these all play a role. But collar trauma is a modifiable risk factor. It is something you can change. And most dog guardians have never been told this.
What You Can Do
1. Switch to a safe, perfectly fitted harness. Permanently.
This is the single most important thing you can do. A well-fitted harness removes the source of compressive pressure from the neck entirely. Every walk without collar pressure is a step toward allowing the cervical spine to decompress and the nervous system to begin healing. I recommend a no-pull, front-clip harness. I evaluated many of them and here is the one I use, love and trust.
2. Have the neck and spine assessed by a trained vet or an animal chiropractor, physical therapist, or osteopath.
Misalignment in the cervical spine does not correct itself. A skilled practitioner can restore proper alignment, reduce nerve compression, and support the body's ability to heal. If adjustments are not holding, combining chiropractic care with physiotherapy and acupuncture often produces better, longer-lasting results.
If you have access to cold laser therapy, it can make a big difference as a treatment or preventive modality. I have used laser on my dog Pax and my own back, neck and shoulder and have seen a clear difference.
3. Support the body's defences nutritionally.
The nervous system and immune system need the right raw materials to recover:
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- MitoBoost (NMN + TMG) supports cellular energy and resilience in tissues whose nerve supply has been under chronic stress
- FeelGood Omega delivers anti-inflammatory omega-3s to help calm the inflammatory environment
- GreenMin provides whole-food minerals that immune cells depend on to function properly
- A fresh, species-appropriate diet is the non-negotiable foundation underneath all of this
4. Reduce your dog's toxic burden.
Pesticide-treated lawns, chemical flea and tick products, and heavily processed food all add to the inflammatory load. Cleaning up the environment works hand-in-hand with cleaning up the nervous system.
5. If your dog has been diagnosed with any tumor — have the back and neck assessed.
The tumor's location helps identify which nerve pathways deserve the most attention, but the principle holds everywhere: a healthy, unimpeded nervous system is part of the terrain the body needs to defend itself against abnormal cell growth.
Here is the energy line chart for clarification:
I have been saying this for twenty years. I was told it was speculative and pseduoscience. I kept saying it because I kept seeing it — in patient after patient, in pattern after pattern — and because the anatomy made it impossible to dismiss.
I am so relieved that in 2025, the research finally caught up.
The nervous system is now confirmed, by multiple independent research groups, to play a direct, causal role in whether cancer starts, progresses, and whether the body can fight back.
A good safe front clip harness is not just a training tool. In the most literal sense, it is a cancer-prevention device.
Your dog cannot tell you their neck and back hurts. They cannot tell you that years of leash walks have slowly built a pro-inflammatory environment in their body. But they show you — through paw licking, front leg stiffness, a tumor at the toe, or a mass found at a routine check-up — and they trust you to look deeper than the symptom.
Look at the neck and back. Assess it, adjust it, strengthen it. Addressing the root cause supports the whole body.
That is how we give our dogs the longest, healthiest lives possible.
References:
Giampietri C, Pizzichini E, Somma F, Petrungaro S, De Santis E, Rahimi S, Facchiano A, Fabrizi C. Roles of Peripheral Nerves in Tumor Initiation and Progression. International Journal of Molecular Sciences. 2025 Jul 22;26(15):7064. doi: 10.3390/ijms26157064. PMID: 40806192; PMCID: PMC12346448.pmc.ncbi.nlm.nih+1
Fu Y, Ge Z-S, Cao Q-Y, Li Z-H, Zhang A, Zhu H-D, Teng G-J. Peripheral Nerves in Cancer: Regulatory Roles and Therapeutic Strategies. MedComm. 2026 Jan 18;7(2):e70594. doi: 10.1002/mco2.70594. PMID: 41556039; PMCID: PMC12812333.
MD Anderson Cancer Center research group. Cancer-Induced Nerve Injury Promotes Resistance to Anti-PD-1 Therapy. Nature. 2025 Aug 19. doi: 10.1038/s41586-025-09370-8.
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